Process of preparing metallic filaments.



INITED STA-'ras PATENT OFFICE.

ROBERT H. HENDERSON, OF EAST ORANGE, NEW-JERSEY, ASSGNOR TO WESTING- HOUSE LAMP COMPANY, A GORPORATION OF PENNSYLVANIA.

rnocnss or PREPARING METALLIC FiLAMENms.

Specification of Lcttersillatent.

Patented Feb. 41, 1916.

Application led December 5, 1910. Serial No. 595,629.

To all whom 'it may concern:

soN, a. citizen of the United States, and a resident of East Orange, inthe county of Essex and State of New Jersey, have 1n' vented a new and useful Improvement in ticularly desirable material for use in the manufacture lof filaments for incandescent lamps, because of the very high efficiency of lamps having such filaments, but trouble has been experienced in the use of tungsten, as heretofore produced in the form of filaments, by reason of itsjbrittle and fragile f character.

According to the' present invention, I propose to subject sintered filamentary tungsten, such as is now -ordinarily used for lamp filaments, or another metal or a combination of metals or substances which are -not sufliciently ductile at ordinary Atempera.-

tures for practical-purposes,suchastitanium,

zirconium, uranium,'chromium and silicon,

to a treatment which will render it4 much more tough and durable, and generally more satisfactory for use in incandescent lamps than it is before subjection to suchtreat? ment.' The treatment consistsin heating the filamentary material to a high temperature :to render it plastic, and at the same time compacting or compressingI its particles into a 'smaller space or diameter, as by drawing it through a die, or swaging it, the filament being thus rendered more compact and homogeneous in texture and its physical-char acter being so modified as to render it more tough.

It has been proposedto reduce tungsten Wire to a small diameter by drawing .it through dies, while the wire is heated to a low temperature. This, however, is not done Mplied, may

5 terial Ithat l forthe purpose of compacting the wire, but 1s 1n all respects similar to the ordinary process of drawing fine metal wires through dies, a slight amount of heating being necessary 1n order to get the tungsten to draw at all, as it is practically non-ductile Processes of. Preparing Metallic Filaments,

when cold. It is, therefore, necessary in the said process, as in all wire-drawing operations, to employ a great number of dies in Y order to reduce the Across-section of the material very' gradually. The present in vention, however, differs essentially in principle from the lprocess described above, the purpose being to force the individual metallic particles composing the filament into very close contact, or in other words, to vobtain a close actual welding together of these particles, which can only be gotten by subl jecting them to a"mechanical compacting process, such as drawing through a die, at a .high temperature, while the particles are in a highly plastic condition', so that they can easily weld together. On this account the aim is not to obtain a very gradual, but rather a sudden reduction ofthe original diameter of the filament under treatment, and 'this can' be attained on account of the high temperature at which the operation is carried out. y ','Ihe single figure ofA the accompanying drawingis a view, in elevation and in section, of simple and suitable apparatus foi` practising my invention.

The vfilamentary material l, to which the treatment of the present invention is ap be obtained from any suitable source", in either short or long lengths, as desired, but Iprefer to usel fllamentary material that is produced continuously and inv j set forth in .an application Serial No.

486,925, filed March31, 1909, by Harry D. Madden, and William G. Houskeeper, assigned tothe Westinghouse Lamp Company. and patented June 2, 1914, No. 1,099,095, and I also prefer to attach the means for practising my process directly tothe machine set forth in the said patent. The purer the mais used in the operation ofthis machine, the better will be. the results ob- 'Htained by its use,-particularlv in connection with the present process. The filamentary otherwise may be passed through two spaced and apertured terminal devices 2 and 3 that su. y

. material obtained fromthe said machine or are suitably connected to an electric circuit 1r-5, and the'apertures of which are filled with mercury that isy held in place by its surface tension and its capillary attraction for the edges of the aperture, Which are preferably amalgamated. A current passed through the filament from the one terminal device to the other raises the temperature of the intermediate portion of the filamentto the required degree. While the ilamentary material is thus heated it is passed through one or more dies 6 having apertures of smaller diameter than that of the lamentary material in its original condition. In.

order to start the ilamentary material through the die, its end must be reduced in diameter to something less than that of the aperture in the die, and, to this end, it may be heated and stretched or compressed, or it may be treated chemically, as by'partial oxidation, in order to remove its outer portions. The filament may be drawn through the die by applying tension to it at its lower end by any suitable means, such as a Weight upon which gravity acts, or by means of any suitable mechanical device.

The compacting of the filament, While highly heated, may be effected by other lmeans than a die, if desired, as by sWaging,

by impact, or otherwise, and the filamentary material may be heated otherwise than electrically.

A The physical characterlstics of the filamentary material may be improved not only by its mechanical compacting at a high tem` perature either befo re or after the application to it of aslnterlng temperature, but also by the application to it after it is sintered of a thermal treatment adapted to eiect the desired physical changes, such as rendering it more ductile and pliable.

I claim as my invention:

l. The process of'preparing iilamentary structures containing,r a metal having a high fusing point which consists in first' producing the material in filamentary Jform,

and then heating the same While mechanically Working it.

2. The process of preparing .ilamentary structures consisting of a metal having a high fusing point Which consists in first producing the material in ilamentary form and then heating the same to a high temperature and mechanically compacting it While heated.

The process of treating ilamentary a ROBERT H. HENDERSON.

Witnesses:

OTTO S. SGHAIRER, CHARLES E. KELLY.. 

